### Question

Books say that heat transfer in an adiabatic process is equal to 0. How can this be if there is a change in temperature?

You are probably making the common mistake among students by not realizing that heat and temperature are two completely different things.

Heat is a quantitative measurement of energy whereas temperature is a qualitative measurement which indicates the warmth or coldness of an object.

In an adiabatic process, there is no heat transfer to or from the system, and therefore change in entropy = 0. Temperature, however, can increase or decrease despite the lack of heat flow. For example, take an insulated piston cylinder device containing some arbitrary gas (common example in thermodynamics problems). If you were to push the piston down (thus compressing the contents of the cylinder), the temperature of the gas in the cylinder would increase. If the piston was pulled out (thus expanding the gas) the temperature would decrease. In either case, no heat would flow to or from the system, but the temperature would change approximately according to the relationship PV=nRT (for the most general cases)

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### Science Quote

'In a way science is a key to the gates of heaven, and the same key opens the gates of hell, and we do not have any instructions as to which is which gate. Shall we throw away the key and never have a way to enter the gates of heaven? Or shall we struggle with the problem of which is the best way to use the key?'

Richard Phillips Feynman
(1918-1988)